One-Piece Pipe-Ended Adjustable Check Valves Available in a variety of sizes and in materials, Stainless Steel 316 or Brass. One-Piece Pipe-Ended Adjustable Check Valves Benefits N Back Stopped Poppet prevents the spring from being over stressed N Insert prevent blow-out of o-ring N End connections, male and female ISO threads, male and female NPT N Stop Nut helps to contain the insert N O-ring provides leak tight shut-off N Spring is adjustable, a wide range of springs are available for the cracking pressure in the range from 3 psig to 600 psig N Adjusting screw sets desired cracking pressure N Locking screw maintains setting N One-Piece Body made from bar stock